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RA: 07h 41m 42s
Dec: −14° 49′ 0″
Ch: MSA:295, U2:274, SA:12
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22r
Mag: B=6.33, V=6.1
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Discovered by Messier in February 1771, he partially resolved the cluster and thought it contained some nebulosity.
In the Appendix to the 1912 'Scientific Papers of Sir William Herschel' this object is described as "1786, March 19, 20 feet telescope, a beautiful, very rich, compressed cluster of stars of various magnitudes."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "beautiful circular group of small stars about half a degree in diameter: a little preceding the group round 4, nearer to it than NGC 2422. NGC 2438, a feeble neb. on its northern verge, is in Lassell's 20-foot reflector 'an astonishing and interesting object.'; he and the E. of Rosse see it annular; also Buffham with a 9-inch reflector."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 27' and the class as 2 2 r.
"! cluster; fairly condensed."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
The RNGC (Sulentic and Tifft 1973) notes that this is a 6.5 mag open cluster.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Journal BAA, 35, p159
Circular, well-defined, 33' diameter, small stars.
Doig, P. (1926) "A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"circular, well defined." He gives the approx. diameter as 29 arcmin.
Vorontsov-Velyaminov, B. (1925) "Catalogue of integrated magnitudes of star clusters", Astron. Nach. 226.195. Comparing the brightness of the cluster with the extrafocal images of stars, he estimates the magnitude as 5.95.
Houston notes: "This cluster of relatively faint stars is nearly 30' across. Although it is listed as of total magnitude 6, estimates are surprisingly discordant. In 1955 I called this cluster magnitude 9, but in 1972 it was rated as no fainter than 7."
Harrington writes: "Scanning this galactic team [M46 & M47] will show just how different from one another open clusters can be. While M47 is a loose grouping, M46 is a densely-packed throng bulging with 100 stars of 9th to 13th magnitude. All appear evenly distributed across the cluster's 20' breadth."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6.1M; 27' diameter; even distribution of 150-plus 10M members; planetary N2438 on N tip (11M; 65" diameter; round and soft); 75' E and a little S of cluster M-47; cluster N2423 is 90' to NW just N of cluster M-47."
"This is a bright open cluster almost a half of a degree in diameter, containing about 100 moderately concentrated stars. As a special treat, the planetary nebula NGC 2438 lies seemingly imbedded in its northeastern edge. The planetary is about 40" in diameter, grayish, and is distinctly ring-shaped. This is a great deep sky double!"
Observer: Alan Shaffer (e-mail: email@example.com)
Instrument: 10-inch Schmidt-Cassegrain reflector Location: Redondo Beach, CA, USA
Light pollution: moderate Transparency: good Seeing: fair
Time: Mon Feb 10 04:30:00 1997 UT Obs. no.: 66
Very large. 104X took up all of eyepiece. Would recommend 60X. Nice full field. Only about 5 stars stuck out in the field. However, this cluster has a few hundred stars. This is a big cluster. I did not detect planetary nebula 2438 due to only fair seeing.
Observer: John Callender
Instrument: 50-mm binoculars Location: Carpinteria, CA, USA
Light pollution: light Transparency: good Seeing: fair
Time: Wed Feb 5 05:15:00 1997 UT Obs. no.: 54
A large, dim glow with no individual members visible in 7x50s.
Steve Coe, observing with a 13" f/5.6, notes: "(M 46) Very bright, very large, rich, somewhat compressed, I estimated 140 stars by counting 35 stars in the northeast quadrant. The cluster in obvious in the 11X80 finder and can be seen naked eye at most of the observing sites in Arizona. Sentinel 13" 7/10--11X80 immediately obvious, 4 stars resolved, a smooth cluster, 150X--very bright, very large, compressed, round, 116 stars counted, many beautiful chains. Planetary on north edge is obvious, light green with central star."
Danie Cronje, observing with 10x50 binoculars, calls it "very large, bright. No very bright stars - 2 or 3 brighter than the rest can be resolved. The rest is a uniform glow, almost like a little cloud. Beautiful. In same binocular field as M47. Incorrectly labeled as M45 in Sky Atlas 2000.0."
Boyden Observatory, Bloemfontein, South Africa
Limiting Magnitude: 6
Air Transparency: Clean & Clear
Light Pollution: City light glaze in far west, 20% moon phase. No material effect on observation.
Weather conditions: Fine, no wind, no clouds
Instrument Used: 8 inch refractor, 30 mm eyepiece, 25' fov.
General impression of object: This is a superb very large open cluster with a large amount of stars (not easily countable) of relatively equal brightness. The planetary nebula NGC 2438 on the edge of the cluster makes it a spectacular sight. Raiting: 8.8/10
General impression of its surrounding area: An impressive area with M47 nearby (binocular) and the planetary nebula in the same telescope view as the cluster.
Description of object:
[Telescope]: This open cluster filled the entire field of view and has numerous stars of almost equal brightness. Though comparable to NGC 3532 and 2477 regarding size and amount of stars, it is not as bright. It almost appears round of shape with no specific patterns quickly identifiable. The planetary nebula on its edge are situated in a darker area of the cluster.
[Binocular]: (12x50) - The cluster appears as a faint fuzzy, almost round object and when imagined to be a clock, a brightening in concentration to the 7/8 o'clock position can be discerned. No individual stars could be identified through the binoculars. It was easy to find, especially due to proximity of M47.
Remarks: (How good or bad the observation was and reasons)
The observation was done under adequate dark skies, concentration and good weather conditions. It did start to set below the telescope walls, but after physical telescope observation was performed.
In a 2-inch refractor this faint, delicate open cluster is rich, evenly spread out, almost circular, and except for two brighter stars breaking the symmetry, its members are of uniform magnitude. Appearing mottled with the 2-inch, a quick glance with binoculars gives the impression of a diffuse, spread-out globular cluster.
This cluster is breathtaking in a 10-inch f.5 at 30x, not because it has bright, sparkling members, but rather because it is a swarming field of light-seeds. The member stars, roughly 10th magnitude, are pretty evenly spread out, the tiny stars gathering together as if for protection. A bright orange star to the southwest shepherds the flock of stars. The cluster is about half a degree in side and contrasts most exquisitely with NGC 2422. The field of view can be positioned in such a manner that just under a half of each cluster is visible at the same time - the one coarse made up of large and small stars mixed together, the other a pure collection of faint points of light. The cluster is even more splendid because of the planetary nebula NGC 2438 on the northern edge.
The cluster bears magnification quite well, and in a 15.5-inch at 220X it shows as a beautiful rich scattering of faintish stars.
Sutherland (Ouberg Quarry)
11x80 tripod mounted binoculars
Conditions: NELM: fainter than 6.0 at the S.pole
Large, extremely rich cluster with three brighter stars (only 9th magnitude) and zillions of faint ones. Appears as a beautiful soft cloud of rough-textured starlight. Compare to NGC 2422 (M47) a degree away. Used Uranometria chart 274 to locate it.
(8-inch Meade, 18mm Super-Wide Angle eyepiece, 36' fov)
Beautiful, very impressive bright and large cluster with curls and dark lanes spread out in a nearly full field. Lovely outstanding hazy nebula embedded towards the north in this cluster. Short lanes of stars with brighter ones in between, even a small dark square to the west with a star inside.
12-inch f5 (EP: 26mm SW, 20mm UW, 7mm UW)
Conditions: The most clear sky possible. Dark moon and stars magnitude 6 and fainter are visible with the naked eye. Excellent clean sky, limited star flickering and brilliant objects. Limiting Magnitude: 6.2.
Open Cluster located in Puppis. Very Bright. Irregular and well grouped as a very large open cluster. By observing this open cluster in my 7mm ultra wide angle eyepiece this cluster fills the whole field of view of plenty of bright stars. This cluster is not separated from the background. 150 individual stars are counted. Most of the stars in this cluster are nearly the same brightness as each other. The stars are strongly concentrated towards each other. There are no starless patches, clumps/ chains of stars are seen. Yes, there is a slight glow of nebulosity around some of the bright stars of this cluster. No obvious prominent stars, coloured stars, or double stars are seen.
2008 March 17, 20:10
Walmer, Port Elizabeth
2.5-inch f/7.6 refractor (EP: 12.5mm 56x 30arcmin fov)
Conditions: Unstable, clear. Moon 84% full, 25 degreers away.
Size=27arcmin, V=6.1. Barely noticeable, faint cluster, generally made up of M8-M9 stars with very little seeable features; although not featureless – NGC 2438 planetary nebula is situated in the southwest portion of the cluster. Hard to define the boundary of cluster; well placed amonst scattered field stars of same magnitude M8-M9. NGC 2437 is a fairly large cluster which forms two outer chains: a western chain running northwest-southeast and an eastern chain northeast to southwest. The whole cluster is characterised by empty starless patches. Bright field star south 1.5-degrees M6.2 HD 61772 useful for navigation, 50arcmin east 4 Puppis M5.9 northeast of 4 Puppis is 2 Puppis M6.
Observing site: Little Tycho Observatory
[7h 41m 48s, -14° 49' 0"] A large cluster of 10...mv stars with a planetary at its north edge.
Telescope: 150mm F5
Limiting magnitude: 4.0
Sky conditions: Clear
This spectacular open cluster contains hundreds of stars fainter than tenth magnitude in an area about 20 minutes of arc in diameter.
In addition the planetary nebula NGC2438 is located east of the northern edge of the cluster.
The Messier objects
The Bennett objects
The Caldwell list
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